1. Field of the Invention
The subject invention relates to a needle guard for enclosing and protecting a needle cannula to avoid accidental sticks and to prevent contamination of the needle cannula prior to use.
2. Description of the Prior Art
A prior art needle cannula is a long narrow metal tube having opposed proximal and distal ends and having a lumen extending between the ends. The distal end of the prior art needle cannula typically is beveled to define a pointed cutting edge that is sufficiently sharp to pierce the skin of a patient or to penetrate a piercable membrane that seals a container of medicine. The proximal end of the needle cannula typically is secured to a structure that will enable fluid communication through the lumen. For example, some prior art needle cannulas are rigidly and permanently connected to the distal end of a hypodermic syringe barrel. Other prior art needle cannulas are securely mounted to a hubs which in turn can be threadedly engaged with the distal end of a prior art syringe barrels.
It is well known that needle cannulas are capable of transmitting disease or infection. For example, an accidental stick with a used needle cannula can transmit disease from the patient on whom the needle cannula had been used. An accidental stick with an unused needle cannula can leave an open wound that is subject to infection if not treated properly. Infection or disease also can be transmitted by means other than an accidental stick. For example contact with an intermediate portion of a needle cannula prior to use can impart contaminants to the outer surface of the needle cannula. These contaminants may be transferred to the patient when the needle cannula is used. Similarly, contact with a side wall region of a used needle cannula can possibly result in a transfer of infectious bodily fluids.
Most needle cannulas are provided with guards or shields that are intended to prevent accidental needle contact. Some needle shields include an elongate rigid shield having an open proximal end and a closed distal end. The shield is mounted over the needle cannula in a distal-to-proximal direction and is frictionally retained on the needle hub or on distal regions of a syringe barrel. The shield can be removed immediately prior to use by exerting a distally directed force on the shield relative to the needle cannula. Shields of this type are very effective and are commonly used for avoiding needle sticks prior to the initial use of a needle cannula. However, it is generally recommended not to use this type of shield after injection because of the possibility of needle sticks during the reshielding process.
Some prior art needle cannulas are provided with a hinged guard. The prior art hinged needle guard may define a generally U-shaped channel having a proximal end that is hingedly articulated to or near the needle hub. The needle guard may be rotated from a first position where the needle cannula is exposed for use to a second position where the needle cannula is partly surrounded by the needle guard. Prior art hinged needle guards are effective for preventing accidental needle sticks. Additionally, prior art needle guards substantially reduce the possibility of inadvertent contact with side wall regions of the needle cannula. However, one longitudinal side of the needle cannula is left exposed by the prior art hinged needle guard. Thus, environmental materials may be able to contact this needle cannula before the initial use.
The prior art hinged needle guard typically will prevent inadvertent contact with any portion of the needle cannula after use. However, the long thin needle cannulas can be bent during use or by inadvertent contact with a hard surface immediately after use. In these situations, the portions of the bent needle cannula may project from the open side of the prior art hinged needle guards. The greatest deviation from a perfect axial alignment is likely to be at the distal tip of the bent needle cannula. Thus, the pointed distal tip could be exposed from the prior art hinged needle guard and could accidentally stick a health care worker who reasonably assumed that the needle was safely enclosed within the prior art hinged guard.
The subject invention is directed to a needle guard assembly for use with a needle cannula. The needle cannula may be of prior art construction, and includes proximal and distal ends. A lumen extends continuously between the proximal and distal ends for accommodating a flow of fluid. The distal end of the needle cannula may be beveled to define a point. The proximal end of the needle cannula may be mounted to structure for enabling fluid flow through the lumen. In a preferred embodiment, as described and illustrated herein, the proximal end of the needle cannula is securely connected to a needle hub. The needle hub may include structure for releasable attachment to a medical implement, such as a hypodermic syringe barrel. In other embodiments, the needle cannula may be mounted directly in a medical implement, such as a hypodermic syringe barrel.
The needle guard assembly of the subject invention includes a guide, a cover and a slide. The guide is securely attachable near the proximal end of the needle cannula. The guide may include a channel for receiving the slide of the needle guard assembly, as explained below.
The cover of the needle guard assembly is an elongate substantially rigid structure having a proximal end and a closed distal end. The cover defines a length that preferably equals or exceeds the length of the needle cannula. Portions of the cover between the proximal and distal ends are of generally U-shaped cross section and are configured to receive the needle cannula therein. The U-shaped portions of the cover may have grooves or similar structure for receiving the slide of the needle guard assembly, as explained below. The proximal end of the cover is joined to the guide at a hinge. The hinge may define a unitary connection between the guide and the cover. However the guide and the cover preferably are separate members that are joined at the hinge. The hinge enables the cover to be hingedly rotated relative to the guide between a first position where the needle cannula is safely received within the U-shaped portions of the cover and a second position where the needle cannula is exposed for use.
The slide of the needle guard assembly is slidably engaged in the channel of the guide for movement between a first position where the slide is adjacent the needle cannula and a second position where the slide is spaced proximally of the needle cannula. The slide may be slidably receivable within the grooves of the cover when the cover is in its first position. Thus, the needle cannula can be completely enclosed between the cover and the slide.
Retaining means may be provided for preventing unintended movement of the slide relative to the guide and/or the cover.
The cover and the slide initially may be in their first positions relative to the guide for enclosing the needle cannula. These relative positions of the cover and slide help protect the needle cannula from contamination prior to use. The needle cannula is placed in condition for use by moving the slide proximally relative to both the guide and the cover and into the second position of the slide. Once the slide has reached its second position, the cover may be rotated away from the needle cannula and into its second position. The needle cannula then may be used in the conventional manner. After use, a thumb or forefinger is used to rotate the cover back to its first position relative to the guide and into substantially surrounding relationship to the used needle cannula. The health care worker then exerts forces on the proximal end of the slide with a thumb or forefinger to urge the slide distally toward its first position. The slide will slidably advance through the channel of the guide and will engage in the grooves of the cover. This distal advancement of the slide in the cover prevents rotation of the cover and simultaneously encloses the one side of the needle cannula that had been left exposed by the U-shaped wall of the cover. Sufficient distal advancement of the slide will completely enclose the cover. Locking structure may be provided for irreversibly maintaining the slide at its distal extreme position to prevent an unauthorized re-exposure of the used needle cannula.